[ARC5] Tuning Cable Question

[Mike Hanz]

On 5/31/2014 8:51 AM, Robert Eleazer wrote:
> Note that with the 274-N receivers, there was a huge increase in the 
> number of tuning cables - from one to three compared to an RU 
> installation.  That may have been a driver, too.

Sounds reasonable.  Every pound counts, I guess.

> It's odd, but that tuning cable that is attached to the coil box on 
> that RU in the F4F-4 picture I sent actually seems to run aft from the 
> radio, toward the tail, and then presumably makes a U-turn and goes 
> back forward to the cockpit.  I wonder if the larger cables had less 
> flexibility and so they had to make big sweeping loops of that sort.

Going out to the shack and grabbing examples of both the MC-124 and 
MC-215 control shafts, it appears empirically that a 4" radius is about 
the smallest you can practicably use with *either* cable without 
deforming the outer sheath.  That's consistent with the warning in the 
SCR-**-183/283 manuals not to plan any tighter turns than 6"R with the 
MC-124.  I couldn't find any guidance for the MC-215 in a quick scan.  
Of course, the tighter the turn, the higher the torque required due to 
friction, and that interferes with the "feel" necessary to do fine 
tuning, so that may have something to do with the long loop in the F4F-4.

73,
Mike